High-resolution simulation of air-breathing rotating detonation engines

Rotating detonation engines (RDEs) use one or multiple spinning detonations to burn propellants in an annular combustion chamber. RDEs are of great interest for hypersonic propulsion as detonation combustion involves a gain in total pressure. Yet, the complex energetic interplay between the leading shock wave and the combustion front in a detonation wave and its propagation speed of around 2000m/s make the experimental investigation of RDEs quite challenging. Numerical simulations are therefore of crucial importance for predicting stable RDE operation at the design stage. Here, we conduct predictive 3D numerical simulations of non-premixed detonation combustion in RDEs using our parallel bock-structured finite volume adaptive mesh refinement framework AMROC, which solves the thermally perfect multi-component Navier-Stokes equations with a detailed chemical model as governing equations on body-fitted curvilinear meshes with dynamic mesh adapation following the detonation fronts. After validating the methodology for a hydrogen-air RDE with available experimental data, we implement constant temperature wall boundary conditions and demonstrate that the number of detonation waves remains unchanged, and that the average detonation velocity deficit rises only slightly, confirming that RDEs can be cooled considerably without significantly affecting the detonation efficiency. Finally, we present simulations with different back pressures of a cooled prototype RDE combustion chamber intended for a laboratory turbine engine running on ethylene and air. The ethylene-air simulations demonstrate that despite a considerably reduced detonation velocity in this very realistic configuration, gains in total pressure at the outlet of 13.3\% and 18.1\% can still be measured, which demonstrates the benefit of the RDE concept for turbine engines quite clearly.